The goal is to reach 90 relationship before the last scene of each romance path.
Each character starts with 15 relationship if you play in Normal level, 20 if you play in Easy and 10 if you play in Hard.
There are 10 scenes with each character, and each right answer usually increases by +5. So if you pick all right answers you can get +50 points, which means even at Hard difficulty you are at 60. Some characters have little more scenes, others less points, to have more harder characters to get. Also, you can get points for a characters also participating in a different romance path. For example one of the scene of Morgan's path can bring +5 to Sebastian, to John, to Jonathan and so on.

I will list only the right choices of each character path, leaving the other one for you to discover

Remember that at regular intervals there are also miniscenes where you can join someone at the tavern and that will give you +1/2 points, or some characters might invite Heileen (this happens towards the end of the game) and if you accept you can get an even bigger boost.

Morgan and John are the easiest characters to romance. Jonathan is mid way and Sebastian surely is the hardest one.

Morgan

Spoiler:

- When talks with Heileen of her friends, if you pick "John" +5
- When they talk about Adam, pick "It is.": +5
- When you watch the stars with Marie, pick "Do nothing.": +5
- When you bring food to Morgan/Juliet and you stumble on the ground pick "Laugh with them.": +2 In the same scene, pick "Eat only a few of the biscuits.": +5
- When Morgan and Sebastian fight at the tavern pick "Get angry at Sebastian.": +5
- When Morgan gives extra money to Heileen in the pirate cove pick "Tell Juliet you're just going to give away the money.": +5
- During the misunderstanding of the engagement ring scene, pick "Wish them luck.": +2
- When the poor child ask money pick "Give him ten gold coins.": +10 and later in the same scene "There's no need.": +5
- When Heileen declares her love to him pick "...have something other women don't. I'm pure.": +10

Jonathan

Spoiler:

- When you pose for him as model pick "Scold her.": +5
- After watching him play chess with Otto pick "Offer to pay for his stay.": +5
- After you lose playing chess with him in your cabin "Compliment him.": +5
- When you're in the kitchen pick "Ask Jonathan to help you.": +5
- When you find the love letter "Don't read it.": +5
- When talking about art as way to get immortal pick "Agree with him.": +5
- When Heileen tries to paint "Calm down and finish the picture.": +5
- When you talk about books "Orlando Furioso by Ludovico Ariosto. I've always been inspired by the morality it promotes.": +10
- When you discover he sold your portrait "You could have asked me for the money!": +5

Sebastian

Spoiler:

- When you follow him and find he is stealing from Morgan "Push him away.": +5
- When he challenges Morgan at throwing knives "Volunteer.": +5
- When he tries to force you to go in the tavern "Threaten him.": +5
- When you are at the tavern with the others "Drink to your heart's content.": +10
- When he asks you to cuddle with him "Accept the offer.": +5 later in the same scene pick "Don't give him anything.": +5
- When you're caught while spying "Play along and be convincing.": +5
- When you follow him and think he's dead "Cry.": +5
- When talking what you'd do with a lot of money "Buy extravagant things for myself.": +5

John

Spoiler:

- When John asks you to help with the sails "Agree to help.": +5
- John offers Heileen some wine "Accept the offer.":
- When John helps cleaning "Don't fasten it.": +5
- When John is waiter and invites you in the kitchen "Eat it in the kitchen.": +5
- When John knocks at the door and is raining "Let him in.": +5
- When he's sad about how he is dressed "Tell him you don't care about the way he looks.": +5
- When he's scared to go with Elias "Give the money.": +5
- When Heileen distributes money on the bridge "Give him more money. He's going to need it, with all those women.": +5

ahah thanks, I've seen it The fact is that I failed to get Morgan, (because indeed I didn't treat him so nice ahah), and even if I've mastered my heileen in teaching, she's not "kind enough" to get the profession ending. The romance image of Morgan appears at about the 300th day, so I wondered if it would have been other scenes in which you could improve your virtues/sins or if playing the other 300 days, was useless

Once you fail a romance, you can advance in other ones, though you probably have already seen most of the scenes. It works like this: there are about 7 scenes each character which you'll always see playing, and the last 3 will be unlocked only if you have a relationship high enough with that specific character. Once you fail, you can unlock those 3 with another one, and so on, to get extra choices.
Like: morgan 8,9,10 => fail, then if you have a good relationship (like >60-70) with John you can see his 8,9,10th scene and so on.
When the yuri version is out, if you get both games effectively you have a bonus to the number of scenes that will play, making the profession ending easier (but I think should be already easy enough right now).

ok, thanks I think it's easy, simply I chose to play my first time in a more "natural way", not watching the consequences of my actions, not playing in order to catch a specific character or to have a specific profession ending, just exploring the game

I think this third game is really awesome and you did a great job, even if, sincerely, 600th days seem to much, because in the end I think you could do everything in 400 days...
You're right if you say "Better give too much days, than too few" but the fact is that when the game ends, you can barely believe it because you thought you had other 300/200 days to play ^_^

I'm not saying it's not long enough, it really is, just that it's kind of tricky to have all these days when truly 400 are really enough I really liked the game, eh, I just wanted to share my opinion ^_^

No worries I understand what you mean. I just thought to leave more in case someone misses the "first romance" and maybe even the second... but perhaps is a bit too much also since previous game of the series were simple visual novel I didn't want to scare players away making the game too hard (in visual novels if you pick the right choices is impossible to "lose").
At which level are you playing by the way?

normal But I repeat that I didn't find it too difficult, in fact I just reloaded some previous saves and I easily got john's ending and then morgan's one, now I want to get some of the professions or other romances, so surely I will play again and again a lot of times eheh. But it's true that I've played to various visual novels previousely so I could easily understand the mechanism of the game. I understand your point, maybe people that are approaching for the first time this kind of game could prefer to have a lot of days in which taste and try a lot of things, but indeed it was what I've done in my first save, playing without thinking too much and I've seen that it's very hard to have the possibility to live 3 romances. Maybe 2, but three, thinking also at all the scenes in which one choice could make you lose points with a guy and gain them with another, It's improbable (in my opinion ^_^).

However I'm very satisfied of my playing by far and I'm just really sad this is the last game of heileen series Maybe one of the first visual novel I've played ^_^
Also, maybe because I'm a nostalgic type, I would have hoped in a sort of epilogue in which we could understand how every character would have end up, but indeed heileen 3 remains one of the best game I've ever played

Thanks! glad you liked it. About being the last of the series, there's an user that is "harassing" (I'm joking) me privately to make another episode I mean I understand what are people's feelings, but while I cannot say that this will be the latest episode for sure, I don't plan to make another for a while. It's a bit like those tv series, the first seasons are great, but after a while even the writers run out of ideas Maybe in a couple of years will think again about it.